• 제목, 요약, 키워드: Random-textured film

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A Study on the Improvement of Light-Extraction Efficiency of Organic Light-Emitting Diodes with a Use of Random-Textured Film (랜덤 택스쳐 필름을 이용한 유기 발광 소자의 광추출 효율 향상에 관한 연구)

  • Kim, Hye Sook;Hwang, Deok Hyeon;Jang, Kyeong Uk;Kim, Tae Wan
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.28 no.7
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    • pp.446-449
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    • 2015
  • An improvement of light-extraction efficiency of organic light-emitting diodes was studied by using random-textured films (RTF). Device was made in a structure of RTF/glass/ITO/TPD/$Alq_3$/LiF/Al. RTF mold was made by spreading PDMS solution on a sandpaper. By pressing this mold on the glass substrate pre-coated with ZPU material, the RTF was obtained. From this study, there was an improvement of external quantum efficiency by about 30% in the device with the random-textured film (RTF 40) compared to that of the reference one.

Study of SF6/Ar plasma based textured glass surface morphology for high haze ratio of ITO films in thin film solar cell

  • Kang, Junyoung;Hussain, Shahzada Qamar;Kim, Sunbo;Park, Hyeongsik;Le, Anh Huy Tuan;Yi, Junsin
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.430.2-430.2
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    • 2016
  • The front transparent conductive oxide (TCO) films in thin fill solar cell should exhibit high transparency, conductivity, good surface morphology and excellent light scattering properties. The light trapping phenomenon is limited due to random surface structure of TCO films. The proper control of surface structure and uniform cauliflower TCO films may be appropriate for efficient light trapping. We report light trapping scheme of ICP-RIE glass texturing by SF6/Ar plasma for high roughness and haze ratio of ITO films. It was observed that the variation of etching time, pattern size and Ar flow ratio during ICP-RIE process were important factors to improve the diffused transmittance and haze ratio of textured glass. The ICP-RIE textured glass showed low etching rates due to the presence of metal elements like Al, B, F and Na. The ITO films deposited on textured glass substrates showed the high RMS roughness and haze ratio in the visible wavelength region. The change in surface morphology showed negligible influence on electrical and structural properties of ITO films. The ITO films with high roughness and haze ratio can be used to improve the performance of thin film solar cells.

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Present Status of Thin Film Solar Cells Using Textured Surfaces: A Brief Review

  • Park, Hyeongsik;Iftiquar, S.M.;Le, Anh Huy Tuan;Ahn, Shihyun;Kang, Junyoung;Kim, Yongjun;Yi, Junsin;Kim, Sunbo;Shin, Myunghun
    • Transactions on Electrical and Electronic Materials
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    • v.17 no.5
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    • pp.275-279
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    • 2016
  • This is a brief review on light trapping in Si based thin film solar cells with textured surfaces and transparent conducting oxide front electrodes. The light trapping scheme appears to be essential in improving device efficiency over 10%. As light absorption in a thin film solar cells is not sufficient, light trapping becomes necessary to be effectively implemented with a textured surface. Surface texturing helps in the light trapping, and thereby raises short circuit current density and its efficiency. Such a scheme can be adapted to single junction as well as tandem solar cell, amorphous or micro-crystalline devices. A tandem cell is expected to have superior performance in comparison to a single junction cell and random surface textures appears to be preferable to a periodic structures.

Electrohydrodynamic Spinning of Random-Textured Silver Webs for Electrodes Embedded in Flexible Organic Solar Cells

  • Yoon, Dai Geon;Chin, Byung Doo;Bail, Robert
    • Journal of the Korean Physical Society
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    • v.70 no.6
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    • pp.598-605
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    • 2017
  • A convenient process for fabricating a transparent conducting electrode on a flexible substrate is essential for numerous low-cost optoelectronic devices, including organic solar cells (OSCs), touch sensors, and free-form lighting applications. Solution-processed metal-nanowire arrays are attractive due to their low sheet resistance and optical clarity. However, the limited conductance at wire junctions and the rough surface topology still need improvement. Here, we present a facile process of electrohydrodynamic spinning using a silver (Ag) - polymer composite paste with high viscosity. Unlike the metal-nanofiber web formed by conventional electrospinning, a relatively thick, but still invisible-to-naked eye, Ag-web random pattern was formed on a glass substrate. The process parameters such as the nozzle diameter, voltage, flow rate, standoff height, and nozzle-scanning speed, were systematically engineered. The formed random texture Ag webs were embedded in a flexible substrate by in-situ photo-polymerization, release from the glass substrate, and post-annealing. OSCs with a donor-acceptor polymeric heterojunction photoactive layer were prepared on the Ag-web-embedded flexible films with various Ag-web densities. The short-circuit current and the power conversion efficiency of an OSC with a Ag-web-embedded electrode were not as high as those of the control sample with an indium-tin-oxide electrode. However, the Ag-web textures embedded in the OSC served well as electrodes when bent (6-mm radius), showing a power conversion efficiency of 2.06% (2.72% for the flat OSC), and the electrical stability of the Ag-web-textured patterns was maintained for up to 1,000 cycles of bending.

Fabrication of Viewing Angle Direction Brightness-Enhancement Optical Films using Surface Textured Silicon Wafers

  • Jang, Wongun;Shim, Hamong;Lee, Dong-Kil;Park, Youngsik;Shin, Seong-Seon;Park, Jong-Rak;Lee, Ki Ho;Kim, Insun
    • Journal of the Optical Society of Korea
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    • v.18 no.5
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    • pp.569-573
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    • 2014
  • We demonstrate a low-cost, superbly efficient way of etching for the nano-, and micro-sized pyramid patterns on (100)-oriented Si wafer surfaces for use as a patterned master. We show a way of producing functional optical films for the viewing angle direction brightness-enhancement of Lambertian LED (light emitting diode)/OLED (organic light emitting diode) planar lighting applications. An optimally formulated KOH (Potassium hydroxide) wet etching process enabled random-positioned, and random size-distributed (within a certain size range) pyramid patterns to be developed over the entire (100) silicon wafer substrates up to 8" and a simple replication process of master patterns onto the PC (poly-carbonate) and PMMA (poly-methyl methacrylate) films were performed. Haze ratio values were measured for several film samples exhibiting excellent values over 90% suitable for LED/OLED lighting purposes. Brightness was also improved by 13~14% toward the viewing angle direction. Computational simulations using LightTools$^{TM}$ were also carried out and turned out to be in strong agreement with experimental data. Finally, we could check the feasibility of fabricating low-cost, large area, high performance optical films for commercialization.

Effect of Surface Pyramids Size on Mono Silicon Solar Cell Performance

  • Kim, Hyeon-Ho;Kim, Su-Min;Park, Seong-Eun;Kim, Seong-Tak;Gang, Byeong-Jun;Tak, Seong-Ju;Kim, Dong-Hwan
    • Proceedings of the Materials Research Society of Korea Conference
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    • pp.100.2-100.2
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    • 2012
  • Surface texturing of crystalline silicon is carried out in alkaline solutions for anisotropic etching that leads to random pyramids of about $10{\mu}m$ in size. Recently textured pyramids size gradually reduced using new solution. In this paper, we investigated that texture pyramids size had an impact on emitter property and front electrode (Ag) contact. To make small (${\sim}3{\mu}m$) and large (${\sim}10{\mu}m$) pyramids size, texturing times control and one side texturing using a silicon nitride film were carried out. Then formation and quality of POCl3-diffused n+ emitter in furnace compare with small and large pyramids by using SEM images, simulation (SILVACO, Athena module) and emitter saturation current density (J0e). After metallization, Ag contact resistance was measured by transfer length method (TLM) pattern. And surface distributions of Ag crystallites were observed by SEM images. Also, performance of cell which is fabricated by screen-printed solar cells is compared by light I-V.

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